I. Information Relating to Previous Squalamine Applications
This invention relates to various methods for using squalamine. Squalamine, having the structure illustrated in FIG. 1, is an aminosterol which has been isolated from the liver of the dogfish shark, Squalus acanthias. This aminosterol is the subject of U.S. Pat. No. 5,192,756 to Zasloff, et al., which patent is entirely incorporated herein by reference. Methods for synthesizing squalamine have been devised, such as the methods described in WO 94/19366 (published Sep. 1, 1994). This PCT publication is entirely incorporated herein by reference. This PCT application also relates to U.S. patent Appln. Ser. No. 08/023,347 (filed Feb. 26, 1993), which application also is entirely incorporated herein by reference. Additional methods for synthesizing squalamine also are described in U.S. patent Appln. Ser. No. 08/985,876 filed Dec. 5, 1997, which application also is entirely incorporated herein by reference.
U.S. Pat. Nos. 5,733,899 and 5,721,226 describe the use of squalamine as an antiangiogenic agent. These U.S. patents are entirely incorporated herein by reference. Additional uses of squalamine (e.g., as a sodium/proton exchanger (isoform 3), or NHE3, inhibiting agent and as an agent for inhibiting the growth of endothelial cells) and squalamine synthesis techniques are disclosed in U.S. Pat. No. 5,792,635. This U.S. patent is also entirely incorporated herein by reference.
II. Information Relating to this Invention
About 50,000 new cases of CNS (central nervous system) tumors are diagnosed each year. Of these, about 35,000 are metastatic tumors (e.g., lung, breast, melanomas) and about 15,000 are primary tumors (mostly astrocytomas). Astrocytomas, along with other malignant gliomas (i.e., cancers of the brain), are the third leading cause of death from cancer in persons between the ages of 15 and 34.
Treatment options for a patient with a CNS tumor are very limited. Currently, surgery is the treatment of choice. Surgery provides a definite diagnosis, relieves the mass bulkiness of the tumor, and extends survival of the patient. The only post-surgery adjuvant treatment which is known to work on CNS tumors is radiation, and it can prolong survival. Radiation treatment, however, has many undesirable side effects. It can damage the normal tissue of the patient, including the brain tissue. Radiation also can cause the patient to be sick (e.g., nausea) and/or to temporarily lose their hair.
The other common post-surgery adjuvant cancer treatment, chemotherapy, is relatively ineffective against CNS tumors. Specifically, chemotherapy against CNS tumors with nitrosoureas is not curative. Many other cancer treating agents have been studied and tested, but generally they have a minimal effect on extending survival.
In view of these limited treatment options, the current prognosis for persons with CNS tumors is not good. The median survival term for patients with malignant astrocytomas having surgery and no adjuvant treatment is about 14 weeks. Radiation therapy after surgery extends the median to about 36 weeks. The current two year survival rate for all forms of treatment is less than 10%.
To maximize survival, it is critical to begin treatment in the early stages of CNS tumor development. Typically, the extent of tumor angiogenesis (i.e., blood vessel formation) correlates with survival in the patient. CNS tumors are among the most angiogenic of all human tumors. When the tumor is small, however, it is in an xe2x80x9cavascularxe2x80x9d phase, and its growth is restricted by a diffusion mechanism (i.e., the cells receive their nutrition, etc. by diffusion into the cell). In this phase, the tumor is viable, but not growing, and it is unable to spread. Over time, however, angiogenesis begins and the tumor converts to a xe2x80x9cvascularxe2x80x9d phase. In this phase, perfusion replaces diffusion as the growth mechanism, and tumor growth is exponential (i.e., the tumor has its own blood vessels to provide nutrients, etc.). Mitotic cells cluster around new blood vessels and metastases occur in the vascular phase (i.e., the tumor can spread to other areas in the body). Therefore, by treating the tumor early (before it reaches the vascular phase), one can hope to inhibit metastatic spread as well as control the primary tumor.
Other types of cancer also are difficult to combat by known cancer treatments. Lung cancer kills more Americans annually than the next four most frequently diagnosed neoplasms combined. Estimates for 1994 indicate more than 170,000 new cases of lung cancer and approximately 150,000 deaths (Boring et al.; CA Cancer J. Clin. 1994, 44: 7-26). Approximately 80% of primary lung tumors are of the non-small cell variety, which includes squamous cell and large cell carcinomas, as well as adenocarcinomas.
Single-modality therapy is considered appropriate for most cases of early and late stage non-small cell lung cancer (NSCLC). Early stage tumors are potentially curable with surgery, chemotherapy, or radiotherapy, and late stage patients usually receive chemotherapy or best supportive care. Intermediate stage or locally advanced NSCLC, which comprises 25% to 30% of all cases of NSCLC, is more typically treated with multimodality therapy. This is a stage of tumor development when angiogenesis is a very important factor. New blood vessels are needed to support further tumor growth and for the development of metastases. Therefore, this stage is amenable to treatment with antiangiogenic agents to prevent the development of new blood vessels. The efficacy of this therapy can be further improved by the combination of the antiangiogenic therapy with cytotoxic chemotherapy or radiation therapy to eliminate existing tumor.
Breast cancer also presents treatment difficulties using known agents. The incidence of breast cancer in the United States has been rising at a rate of about 2%/year since 1980, and the American Cancer Society estimated that 182,000 cases of invasive breast cancer were diagnosed in 1995. Breast cancer is usually treated with surgery, radiotherapy, chemotherapy, hormone therapy, or combinations of the various methods. Like other solid tumors, breast cancer requires the development of new blood vessels to support its growth beyond a certain size, and at that stage in its development, it will be amenable to treatment with antiangiogenic agents.
A major reason for the failure of cancer chemotherapy in breast cancer is the development of resistance to the cytotoxic drugs. Combination therapy using drugs with different mechanisms of action is an accepted method of treatment which prevents development of resistance by the treated tumor. Antiangiogenic agents are particularly useful in combination therapy because they are not likely to cause resistance development since they do not act on the tumor, but on normal host tissue.
Prostate cancer is another cancer for which new therapies are needed. Despite the prevalence of prostate cancer as the most frequently diagnosed malignancy among American men, mechanisms of prostate carcinogenesis are poorly understood. The multiplicity of factors involved in the development, proliferation, and dissemination of human prostate cancer, as well as their relationships and interaction with one another, magnify the difficulty of treatment.
Both prostate tumor cell growth and metastasis require adequate metabolic support as well as vascular access and thus rely on angiogeneis. The prostate cancer cell-extracellular matrix (ECM)/stromal relationship is also significant to the growth and spread of human prostate cancer. Of the numerous growth factors present in the ECM, b-FGF (basic fibroblast growth factor, also known as FGF-2) and VEGF (vascular endothelial growth factor) stand out as having been implicated in both inducing a malignant phenotype and in promoting and maintaining angiogenic processes. Ultimately, the outcome of a patient with prostate cancer largely depends upon the tumor""s capacity for unhindered growth, local invasion, and the establishment of distant metastasis. Thus, anti-angiogenic agents may effectively inhibit the growth and metastasis of such tumors.
Current therapies for prostate cancer focus on inhibiting the androgen agent. Radiation is, as with many cancers, an initial line of treatment, often followed by hormonal therapy. Such hormonal therapy seeks to specifically inhibit the androgen agent. Inhibition can result from either surgical castration or chemical castration with agents such as LHRH (luteinizing hormone releasing hormone) agonists and anti-androgens (such as flutamide, biclutamide, nilutamide, and luprolide). However, these therapies fail in most patients who thereafter present with hormone-refractory lesions. Currently, few therapeutic options exist for men with hormone-refractory prostate cancer, and none offer much durability. At this point, tumor growth can be so accelerated that life expectancy rarely exceeds six months to one year. Indeed, 70% of these patients will eventually die of their hormonal refractory disease.
In such patients, who have undergone anti-hormone therapies, the remaining prostate tumor cells are likely undergoing rejuvenated proliferation. Accordingly, anti-angiogenic agents may be most effective at this stage, particularly agents that are most potent on freshly sprouting, young blood vessels, thereby preventing neovascularity and repressing further tumor growth and metastasis.
Ovarian cancer is the most serious gynecologic tumor type. Over 50% of all cancer-related gynecologic deaths are attributable to ovarian cancers, of which 80-90% are epithelial-derived tumors. In 1997 there were 26,700 new cases of ovarian cancer and more than 14,000 deaths. There is a clear genetic component to ovarian cancer. Newly developed detection methods have shown strong correlations between breast cancer, ovarian cancer and expression of genetic markers that include BRCA1 or mutant oncogenes such as aberrant forms of erbB-2 or c-Myc. Another good marker for ovarian cancer of clinical utility is the circulating analyte CA 125, for which serum levels generally reflect the state of cancer progression. CA125 is often monitored in ovarian cancer, although it is not a validated marker. There is also a hormonal influence on cancer risk in ovarian cancer, as is seen in breast cancer
About one-third of ovarian cancer patients present with localized disease. Early stage ovarian cancer is treatable with some combination of surgery, radiation and chemotherapy; the 5 year survival rate for localized ovarian cancer is greater than 80%. However, the 5 year survival rate for metastatic stage III or IV ovarian cancer is less than 20%. It is these advanced patients, those for whom the ovarian tumors escape the ovarian capsule and invade intraperitoneal surfaces, who require the most aggressive therapy yet benefit only marginally with chemotherapy. The first line chemotherapeutic treatment for ovarian cancers has been the use of platinum-based regimens for over a decade. With the advent of newer agents such as the taxanes (paclitaxel, docetaxel), gemcitabine, newer vinca alkaloids (vinorelbine), and topoisomerase inhibitors (topotecan, irinotecan), combination chemotherapy has become more widely explored in advanced ovarian cancer patients. The combination (sequential or concurrent) of a taxane and a platinum agent is the present standard first line treatment for advanced ovarian cancer patients. However, the poor prognosis for these patients despite the aggressive use of chemotherapy and surgery (with or without radiotherapy) suggests the further addition of non-cytotoxic agents such as an angiogenesis inhibitor would be beneficial.
There are recent estimates that the incidence of deaths due to liver cancer worldwide could be as high as 106 or more per year. Hepatocellular carcinoma (HCC) or hepatoma is the most common liver cancer tumor and is a tumor type that is closely associated with chronic hepatitis B or hepatitis C infection. The high frequency of hepatitis viral infections observed in Asia and Africa make these regions the sites of the largest number of liver cancers, most of which are HCC tumors. Although viral infection is considered essential for predisposition to HCC, infection alone is not the only contributing factor to hepatocellular transformation and proliferation. By comparison, there were 13,500 deaths of liver cancer in 1992 in the United States, of which two-thirds were HCC.
The prognosis for liver cancers is universally poor with the minor exception of those tumors which are only locally invasive and are located favorably for curative surgical removal. For locally advanced disease, limited efficacy has been seen with interferon therapy, polyprenoic acid (vitamin A derivative), 5-fluorouracil or cryoablation. No meaningful combination chemotherapy has proven itself in human trials for HCC to date, but the urgent clinical need continues to drive experimental evaluation of various therapeutic approaches. A recent report (LX Qin et al., Ann Acad Med Singapore 28,147-51 (1999)) suggests that angiogenesis inhibitors can inhibit hepatoma tumor growth in mouse xenograft tumor models and may be candidates for the control of recurrence and metastasis after HCC resection. It therefore is a reasonable approach to consider combining treatment of HCC patients not eligible for curative surgery with an angiogenesis inhibitor and an active second modality such as xcex1-interferon, a cytotoxic agent such at 5-fluorouracil, or a vitamin A derivative.
Pediatric tumors are among the less common tumors seen in the oncology clinic. There were only 7700 children under the age of 15 reported with cancer in 1994. Although this only represents about 1% of the entire cancer population, much attention is given by oncologists to the special problems and to the social benefit associated with treating cancer among children. The most common solid tumor among affected children is neuroblastoma, which is of neuroendocrine origin.Other solid tumors among children are Wilms"" tumor, rhabdomyosarcoma and retinoblastoma. Neuroblastomas represent 9% of all childhood cancers, but 15% of pediatric cancer deaths. Many pediatric tumors have a genetic basis; for example, it is estimated that perhaps 20% of neuroblastomas are genetic in nature.
Neuroblastomas most commonly are seen in the abdomen, many of these being found in the adrenal gland. The median age at diagnosis for neuroblastoma patients is 2 years. Surgery can be curative in early stage neuroblastomas, but most children present with metastatic disease. Even in children with minimal residual disease following surgery, recurrences are seen in more than half of all patients. Clinical trials have emphasized the positive value of using post-surgical chemotherapy with or without radiation therapy. Neoadjuvant chemotherapy is also commonly used with neuroblastoma patients, but it is more common to use chemotherapy in the adjuvant setting. Neuroblastoma is a particularly difficult tumor to treat, and platinum-based regimens are frequently used in first or second-line treatments. The chemotherapeutic regimens for pediatric patients are highly aggressive, often involving megatherapy with 4-6 cytotoxic agents. Neuroblastoma tumors represent an interesting opportunity for antiangiogenic therapy as neuroblastomas are highly vascular, grow quickly and metastasize rapidly. Antiangiogenic therapy for neuroblastoma may allow new aggressive combination chemotherapy treatments involving cytostatic agents since they are anticipated to provide minimal additional toxic side effects and should not diminish the efficacy of the cytotoxic agents to which they are matched.
It is an object of this invention to provide a method for treating malignant and cancerous tumors using squalamine, in combination with other, conventional cancer treating agents. Although the invention can be applied to any responsive tumor, in particularly preferred aspects of the invention, the tumors treated are found in the CNS, lung, breast, ovary, liver, neuroendocrine and prostate tissues.
In one method according to the invention, squalamine is used in combination with conventional cancer treatments to treat tumors. Such conventional cancer treatments include the use of cytotoxic agents as well as anti-hormonal agents. In one embodiment, the tumor is treated by administering an effective amount of a cytotoxic chemical compound or a combination of cytotoxic compounds in a first treatment procedure, and an effective amount of squalamine is administered in a second treatment procedure.
In this method, the cytotoxic chemical compound used in the first treatment procedure is a conventional cancer treating agent. Preferable agents include a nitrosourea, cyclophosphamide, doxorubicin, epirubicin, 5-fluorouracil, topotecan and irinotecan, carmustine, estramustine, paclitaxel and its derivatives, and cisplatin, carboplatin, iproplatin and related platinum compounds. These conventional cancer treating agents are well known to those skilled in this art. Note, M. C. Wiemann and Paul Calabresi, xe2x80x9cPharnacology of Antineoplastic Agents,xe2x80x9d Medical Oncology, Chapter 10, edited by Paul Calabresi, et. al., McMillan Publishing (1985). Medical Oncology is entirely incorporated herein by reference. One particularly preferred nitrosourea is BCNU, which also is known as carmustine. Another preferred cytotoxic agent is a platinum compound such as carboplatin, iproplatin or cisplatin, and yet another is cyclophosphamide. Other conventional cytotoxic chemical compounds, such as those disclosed in Medical Oncology, supra., can be used without departing from the invention.
In another embodiment the tumor is treated by first inhibiting hormones that affect the tumor and then administering an effective amount of squalamine in a second treatment procedure. In one aspect, the hormones may be specifically inhibited. When the tumor is of the prostate, the hormone inhibition may result from orchiectomy, i.e., the removal of one or both testes. Orchiectomy may result from surgery or from the administration of chemical agents such as LHRH (luteinizing hormone releasing hormone) agonists and/or anti-androgens (such as flutamide, biclutamide, nilutamide or luprolide).
The cytotoxic and anti-hormonal chemical compounds administered in the first treatment step may be administered by any conventional technique used in the art (i.e., oral, subcutaneously, intralymphatically, intraperitoneally, intravenously, or intramuscularly). In one embodiment of the invention, the cytotoxic chemical compound (preferably BCNU, cisplatin, or cyclophosphamide) is administered intravenously. Likewise, squalamine can be administered by any conventional administration method known in the art, such as those mentioned above. Subcutaneous injections of squalamine one or two times a day are used in one embodiment of this invention. Intravenous administration of squalamine one or two times a day are used in another embodiment of the present invention.
The first treatment procedure with the cytotoxic chemical or anti-hormonal compound may take place prior to the second treatment procedure (using squalamine), after the second treatment procedure, or at the same time as the second treatment procedure. Furthermore, the first treatment procedure may be completed before the second treatment procedure is initiated (or vice versa). In one embodiment of the invention, the first treatment procedure is a one time intravenous administration of a cytotoxic chemical or anti-hormonal compound (i.e., BCNU, cisplatin, or cyclophosphamide), and the second treatment procedure involves daily subcutaneous injections of squalamine.
In addition, the invention encompasses the use of squalamine together with cytotoxic compounds or antihormonal compounds or the use of two or more of these compounds with squalamine. The invention also encompasses the use of squalamine together with a cytostatic agent or the use of these two treatment modalities with a cytotoxic compound. A cytostatic agent is any chemical compound which is capable of arresting the growth of tumor cells or normal stromal cells in a tumor but which is not toxic at pharmacologically active concentrations. A pharmacologically active concentration of a cytostatic agent used in the first treatment procedure may be any know cell growth modulator, but it is preferably the calcium pump inhibitor carboxyamidotriazole.
In a second method for treating a tumor according to the invention, the first treatment procedure is a radiation treatment, which may be one or more conventional radiation modalities, using a conventional radiation treatment regimen known to those skilled in the art. The tumor is exposed to radiation in this first treatment procedure. In a second treatment procedure, an effective amount of squalamine is administered to treat the tumor. Appropriate timing of the radiation treatment procedure with respect to the squalamine treatment regimen can be determined by those skilled in the art through routine experimentation in order to provide effective tumor treatment.
In addition to radiation and squalamine treatments, the tumor also may be treated with one or more cytoxic chemical or anti-hormonal compounds in a third treatment procedure. Further, in addition to radiation and squalamine treatments, the tumor also may be treated with one or more cytostatic chemical compounds in a third treatment procedure. The cytostatic agent used in the third threatment procedure may be any known cell growth modulator which is not cytotoxic, but it is preferably the calcium pump inhibitor carboxymidotriazole. It is additionally envisioned in the present embodiment of the invention that tumors treated with radiation, squalamine and a cell growth modulator may also be treated with one or more cytotoxic chemical compounds in a fourth treatment procedure.
Of course, the invention also relates to the use of both cytotoxic chemical and/or anti-hormonal compounds in addition to radiation, or any other combination of treatment methods.